remove yt-dlp, fix captions PO Token issue, fix 429 retry logic

- Remove yt-dlp entirely (modules, routes, settings, dependency)
  Was blocking page loads by running synchronously in gevent
- Fix captions: use Android client caption URLs (no PO Token needed)
  instead of web timedtext URLs that YouTube now blocks
- Fix 429 retry: fail immediately without Tor (same IP = pointless retry)
  Was causing ~27s delays with exponential backoff
- Accept ytdlp_enabled as legacy setting to avoid warning on startup

settings.py

@@ -340,15 +340,6 @@ Archive: https://archive.ph/OZQbN''',
         'hidden': True,
     }),
 
-    ('ytdlp_enabled', {
-        'type': bool,
-        'default': True,
-        'comment': '''Enable yt-dlp integration for multi-language audio and subtitles''',
-        'hidden': False,
-        'label': 'Enable yt-dlp integration',
-        'category': 'playback',
-    }),
-
     ('settings_version', {
         'type': int,
         'default': 6,
@@ -359,7 +350,8 @@ Archive: https://archive.ph/OZQbN''',
 
 program_directory = os.path.dirname(os.path.realpath(__file__))
 acceptable_targets = SETTINGS_INFO.keys() | {
-    'enable_comments', 'enable_related_videos', 'preferred_video_codec'
+    'enable_comments', 'enable_related_videos', 'preferred_video_codec',
+    'ytdlp_enabled',
 }